1. Field of the Invention
The present invention relates to an asynchronous transfer mode (hereinafter abbreviated ATM) cell monitoring, more particularly, to an asynchronous transfer mode cell monitoring method in communication Systems and a system thereof which enable to monitor ATM cells which are being transceived (transmitted/received) between a base transceiver system and a base station controller by specific VPI/VCI, errors of ATM cells, and transmission time of the ATM cells.
2. Background of the Related Art
ATM, which is developed from the packet exchange principle, enables to perform high speed operation as fast as circuit switching does by simplifying a method of processing packets which are being transmitted.
Digital information generated from the ATM is split into blocks each of which has constant length. And, the split blocks to which headers of 5 bytes including receiving numbers respectively are transferred. Other blocks similar to the packets are called cells in ATM.
In a network system, the corresponding cell is transferred to the opposite party by finding an address of the destination included in the header by cell unit. In a transfer path, the cells arrived from a plurality of terminals are multiplexed in order of arrival sequence and then transferred to the destinations. It is known immediately that the header information of the cell is transferred from a specific terminal, thereby enabling to make a distinction from the multiplex transfer.
As all the cells are transferred after the division, it is not necessary for a physical line to be occupied by one communication. Namely, it is desirable in the efficiency of using a line that ATM cells are transferred through the single line by being multiplexed. It looks like by the transmitting party that a dedicated line is provided for the cells to reach the opposite party by cell transmission through various lines. Such a line called virtual channel (VC). A number that is called virtual channel identifier (VCI) is designated to the virtual channel.
A single virtual channel is established between one terminal and the other terminal, while a plurality of virtual channels are established between sub systems in a telecommunication network. In such intervals, some of the virtual channels are bound together according to the virtual channel identifier each and then a pack of the bound channels is transmitted to the destined terminal. Such a pack of several bound channels together is called a path.
In ATM, the virtual channels are bound by the VCI, whereby the path is so-called a virtual path having a virtual path identifier(VPI).
FIG. 1 shows a block diagram of an ATM cell monitoring device in an ATM low rate subscriber multiplexing/demultiplexing part of a base station controller according to a related art
Referring to FIG. 1, a mobile telecommunication system comprises a base transceiver station 10, a base station controller 20 controlling the base transceiver station, a mobile switching center 30 constituting an interface point for a user traffic between switching centers.
In an ATM cell monitoring device of an ATM low rate subscriber multiplexing/demultiplexing part in a base station controller according to a related art, as shown in FIG. 1, the base transceiver station 10 and the ATM low rate physical layer board assembly (ALPA) 1 are connected each other via ‘E1’.
And, an ATM low rate subscriber multiplexing/demultiplexing board assembly 2 functions as an interface between an ATM switch in the base station controller 20 and the base transceiver station 10 for data transceiving, thereby multiplexing and demultiplexing an ATM cell.
Moreover, the ATM low rate subscriber multiplexing/demultiplexing board assembly 2 transmits an ATM cell to an ATM switch in the base station controller 20 and makes an SOC (start of cell) signal of the ATM cell become low active whenever transmitting a first byte of the ATM cell of 53 bytes, thereby storing the number in a dual port RAM (DPRAM) whenever the SOC signal becomes active. The location written in the dual port RAM is distinguished by indexing with VPI/VCI, which is read by a CPU of the ATM low rate subscriber multiplexing/demultiplexing board assembly 2 to ascertain how many cells have passed through by the corresponding VPI/VCI.
In accordance with the number of storage in the dual port RAM, as mentioned in the above explanation, the number of the ATM cells inputted in the base station controller and the other number of the ATM cells outputted from the base station controller are monitored. Unfortunately, the ATM cell monitoring device according to the related art only monitors how many ATM cells are transmitted and received when transceiving an ATM cell consisting of 53 bytes yet fails to monitor an error of the transceiving ATM cell and a delay time of the cell transmission from the base station controller to the base transceiver station.